1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device including a crown-type capacitor.
2. Description of the Related Art
Higher integration of memory cells has been desired in a semiconductor memory device, such as DRAM device (Dynamic Random Access Memory). In order to achieve the higher integration of the memory cells, it is necessary to increase the capacitance per the area which each cell capacitor of the memory cells occupies. One of the techniques for obtaining a higher capacitance for the cell capacitors is to form crown-type capacitors in the memory cell area. For forming the crown-type capacitors, a bottom electrode film is formed along the bottom and sidewall of cylindrical through-holes formed in a thick insulated film, referred to as cylinder-receiving film in this text, followed by removing the thick insulation film to thereby leave cylindrical bottom electrodes.
The capacitance of the crown-type capacitors may be increased by increasing the height of the cylindrical bottom electrodes to increase the surface area of the bottom electrodes. However, there occurs a problem in the conventional technique that the bottom electrodes are liable to incline and collapse toward the adjacent bottom electrodes along with the increase of the height of the bottom electrodes, thereby causing a short-circuit failure.
A technique for forming a spacer ring, or insulating spacer, in the vicinity of the top of the bottom electrodes is proposed to solve the above problem of the short-circuit failure. The insulating spacer formed in the vicinity of the top of the bottom electrodes prevents the short-circuit failure even in the case of inclination or collapse of the bottom electrodes. The technique for forming the insulating spacers is described in, for example, Patent Publication JP-2005-150747A.
The process, described in the above publication, for forming the insulating spacers includes the steps of forming a bottom electrode film on the bottom and sidewall of cylindrical holes, and embedding an insulating film in the cylindrical holes with an intervention of the bottom electrode film. After removing the surface portion of the wafer as a whole to divide the bottom electrode film into a plurality of bottom electrodes, the upper portion of the cylinder-receiving film and the embedding insulating film is etched for removal thereof, to form a step difference between the remaining portion of the insulating films and top of the bottom electrodes.
An insulating spacer film is then deposited to cover the step difference on the wafer, followed by etch-back thereof to leave the insulating spacers along the inner and outer surfaces of the bottom electrode. Subsequently, the cylinder-receiving film and embedding insulating film are removed to expose the cylindrical bottom electrode.
The technique as described above provides the insulating spacers on the inner side and outer side of the cylindrical bottom electrodes, because the top portion of both the cylinder-receiving film and embedded film is removed during forming the step difference. The insulating spacers formed inside the cylindrical bottom electrodes reduces the inner diameter of the opening of the cylindrical bottom electrodes, thereby causing an obstacle against forming the capacitor insulator film on the inner surface of the cylindrical bottom electrodes.